The present invention relates to an optical scanning apparatus and, more particularly, to a multi-resolution transmissive and reflective optical scanner.
Optical scanning apparatuses are currently in great demand as a result of the rapid development of high speed, low cost imaging devices and the ever decreasing cost of personal computers. Optical scanners, in general, are capable of reflective and/or transmissive scanning of documents, photographs and the like, whereby reflective scanning is used with opaque objects such as photographs and transmissive scanning is used with transparent objects, such as slides and the like. Reflective scanners project light onto the side of the object to be scanned. The reflected light is viewed by an optical sensor which converts the reflected light into digital code. The code is then transmitted to the operator""s computer for further processing. Transmissive scanners operate on the same principle except that light is projected through the transparent object being scanned. A great demand exists for high quality, low cost, low maintenance, easy to calibrate, versatile optical scanners capable of both high and low resolution reflective and transmissive scanning.
A conventional scanner typically has scanning platform(s) and a chassis including an optical sensor, a lens assembly, a plurality of mirrors and light source(s), mounted on rails inside the scanner housing and driven by a motor within the housing to scan along the length of the document being placed on the scanning platform. During reflective operation the light source projects light upon the portion of an opaque object within the field of view of the optical sensor, with the scanner chassis moving incrementally lengthwise under a reflective scanning platform and scanning an image line by line. During transmissive operation, another light source, preferably housed under a transmissive scanning platform, within the scanner housing, provides light through a portion of a transparent object within the field of view of the optical sensor. Switching between transmissive and reflective modes may be accomplished by transverse movement of the lens assembly and/or corresponding movement of mirrors within the scanner housing, depending on the nature of object being scanned. Actual switching is controlled by the operator, who programs the scanner for the desired mode of scanning before starting the operation. A scanner which employs movable mirrors only to switch between scanning modes, is described, for example, in U.S. patent application, Ser. No. 08/393,112, filed Feb. 21, 1995 (attorney docket: 5592-1016), commonly owned by applicant, and which is incorporated herein by reference. Such transmissive/reflective scanners provide scanning of objects in one resolution only. Thus, the need exists for a versatile optical scanner capable of multi-resolution transmissive and reflective scanning.
It is an object of the present invention to provide an optical scanning apparatus for multi-resolution reflective and transmissive scanning of objects.
It is an additional object of the present invention to provide an optical scanning apparatus for high and low resolution reflective and transmissive scanning of objects using an optical sensor and a dual-lens assembly.
It is another object of the present invention to provide a reflective scanning platform adapted for the reflective scanning of opaque objects and a transmissive scanning platform adapted for the transmissive scanning of transparent objects, each of the platforms being within the corresponding field of view of the optical sensor.
It is a further object of the present invention to provide optical pathways for interaction with the transmissive/reflective scanning platforms, the dual-lens assembly and the optical sensor.
It is yet another object of the present invention to provide each optical pathway with a transmissive branch, a reflective branch and an optical switch for switching between high and low resolution modes in each branch.
It is still another object of the present invention to provide an optical switch for switching between the transmissive and reflective branches in each optical pathway.
It is still a further object of the present invention to actuate the optical switches in response to an electronic signal generated by a scanner control circuit.
In accordance with the objects of the present invention, an optical scanning apparatus for retrieving images representative of objects is provided with at least one scanning platform capable of holding an object for scanning; an optical sensor; a lens assembly comprising at least two lenses; at least two optical pathways, each pathway including a plurality of mirrors defining a corresponding optical path from at least one scanning platform to said optical sensor through a corresponding one of said lenses; and an optical switch adapted to alternate between said pathways.
More particularly, the present invention provides an optical multi-resolution scanning apparatus for retrieving digital images representative of opaque or transparent objects including a reflective scanning platform capable of holding an opaque object for reflective scanning; a transmissive scanning platform capable of holding a transparent object for transmissive scanning; an optical sensor; a dual-lens assembly comprising a first, relatively high resolution lens and a second, relatively low resolution lens; a first optical pathway including a plurality of mirrors defining an optical path from said reflective scanning platform to said optical sensor through said first lens; a second optical pathway including a plurality of mirrors defining an optical path from said reflective scanning platform to said optical sensor through said second lens; a third optical pathway including a plurality of mirrors defining an optical path from said transmissive scanning platform to said optical sensor through said first lens; a fourth optical pathway including a plurality of mirrors defining an optical path from said transmissive scanning platform to said optical sensor through said second lens; a first optical switch adapted to alternate between a reflective scanning mode and a transmissive scanning mode; and a second optical switch adapted to alternate between said first and second optical pathways, or between said third and fourth optical pathways.
The optical sensor is aligned with the optical pathways; the optical pathways being selectively aligned with the reflective and transmissive scanning platforms in a high or low resolution scanning mode such that the control circuit receives corresponding high or low resolution images of objects being scanned.
An optical switch mirror having an axle attached to a frame secured to the base of the scanner chassis is provided such that rotation of the axle pivotally changes the angular displacement of the optical switch mirror to switch between usage of the relatively low resolution lens and the relatively high resolution lens.
A transmissive/reflective mode optical switch mirror is also provided such that rotation of its axle provides for switching between transmissive and reflective modes of operation and corresponding optical pathways.
Other features and advantages of the invention will become apparent upon review of the appended drawings and detailed description of the invention.